Field of the Invention
The disclosed concept relates generally to a can bodymaker and, more specifically, to a can bodymaker having a redraw assembly actuated by an eccentric journal.
Background Information
Generally, an aluminum can begins as a disk of aluminum, also known as a “blank,” that is punched from a sheet or coil of aluminum. The blank is fed into a cupper. The cupper performs a blank and draw process to create a cup. That is, the blank is formed into a cup having a bottom and a depending sidewall. The cup is fed into one of several bodymakers, which perform a redraw and ironing operation. More specifically, the cup is disposed in a can forming machine at the mouth of a die pack having substantially circular openings therein. The cup is held in place by a redraw sleeve, which is part of the redraw assembly. The redraw sleeve is a hollow tubular construct that is disposed inside the cup and biases the cup against the die pack. More specifically, the first die in the die pack is the redraw die, which is also a part of the redraw assembly. The cup is biased against the redraw die by the redraw sleeve. Other dies, the ironing dies, are disposed behind, and axially aligned with, the redraw die. The ironing dies are not part of the redraw assembly. An elongated, cylindrical ram having a punch at the forward, distal end is aligned with, and structured to travel through, the openings in the redraw die and the ironing dies. At the end of the die pack opposite the ram is a domer. The domer is a die structured to form a concave dome in the bottom of the cup/can.
Thus, in operation, a cup is disposed at one end of the die pack. The cup, typically, has a greater diameter than a finished can as well as a greater wall thickness. The redraw sleeve is disposed inside of the cup and biases the cup bottom against the redraw die. The opening in the redraw die has a diameter that is smaller than the cup. The ram, with the punch as the forward, distal end, passes through the hollow redraw sleeve and contacts the bottom of the cup. As the ram continues to move forward, the cup is moved through the redraw die. As the opening in the redraw die is smaller than the original diameter of the cup, the cup is deformed and becomes elongated with a smaller diameter. The wall thickness of the cup typically remains the same as the cup passes through the redraw die. As the ram continues to move forward, the elongated cup passes through a number of ironing dies. The ironing dies each thin the wall thickness of the cup causing the cup to elongate. The final forming of the can body occurs when the bottom of the elongated cup engages the domer, creating a concave dome in the cup bottom. At this point, and compared to the original shape of the cup, the can body is elongated, has a thinner wall, and a domed bottom. The can body is ejected from the ram, and more specifically the punch, for further processing, such as, but not limited to trimming, washing, printing, flanged, inspected and placed on pallets, which are shipped to the filler. At the filler, the cans are taken off of the pallets, filled, ends placed on them and then the filled cans are repackage in six packs and/or twelve packs cases etc.
The ram moves in a cycle many times each minute. Thus, for each cycle, a cup must be positioned in front of the die pack and clamped by the redraw sleeve. That is, as noted above, the redraw assembly includes the stationary redraw die and the movable redraw sleeve. The redraw sleeve must move forward and back for each cycle. Moreover, the redraw sleeve must “dwell” in the forward location, i.e., clamping the cup, while the ram passes therethrough and moves the cup into the redraw die. That is, the motion of the redraw sleeve includes a forward motion, a dwell, and a backward motion. The redraw sleeve is, typically, moved by a circular cam disposed about the redraw sleeve. The circular cam is a continuous ridge extending inwardly from an outer sleeve, or “outer casing,” disposed about a carrier for the redraw sleeve. The cam, i.e., the continuous ridge, encircles the inner surface of the outer sleeve with portions that are angled forward, not angled (or not substantially angled), and angled backward. The carrier for the redraw sleeve has a cam follower. As the outer sleeve rotates, different portions of the cam engage the cam followers.
Thus, as the portion of the cam that is angled forward engages the cam followers, the redraw sleeve carrier, and thus the redraw sleeve, moves forward; this is the motion that moves the redraw sleeve into the cup and biases the cup against the redraw die. At this point, a non-angled portion of the cam engages the cam followers; this causes the redraw sleeve to dwell in the forward position, i.e., clamping the cup. Continued rotation of the redraw sleeve carrier causes the angled backward portions of the cam to engage the cam followers and the redraw sleeve carrier, and thus the redraw sleeve, moves forward. It is noted that the backward motion of the redraw sleeve occurs, essentially, as soon as the cup is moved into the redraw die and while the ram is extending through the redraw sleeve. Once the ram is withdrawn from the redraw sleeve, a new cup is moved into position in front of the redraw die and the cycle begins again. A device that performs these operations is disclosed in U.S. Pat. No. 5,775,160, which is incorporated by reference.
The outer sleeve upon which the cam is disposed is heavy. This sleeve is actuated by cams, or other mechanical links, that are coupled to the drive mechanism for the ram. In this manner, the motion for the redraw sleeve is linked to the motion of the ram. The components forming the linkage between the ram drive mechanism and the cam must be robust, including being heavy, in order to accommodate the multiple cycles that occur every minute. Because the outer sleeve and other linkage components are heavy, the drive mechanism for the ram must be structured to provide more energy than is required to simply move the ram. Further, all the mechanical linkages from the ram drive mechanism to the redraw sleeve are prone to wear and tear. There is, therefore, a need for an improved actuator for a redraw sleeve.